1. Field of the Invention
The present invention relates to a fuel cell. More specifically, the present invention relates to a fuel cell in which a reactant gas channel can be formed by effectively utilizing a sealing member.
2. Description of the Related Art
There has been developed a solid polymer electrolyte type fuel cell which, for instance, constituted by laminating a plurality of units, with one unit being such that a membrane electrode assembly (MEA) provided with an anode and a cathode at opposite positions with a solid polymer electrolyte membrane inserted therebetween is clamped by separators, and this has been utilized for various practical applications.
In this type of fuel cell, a fuel gas, for example a hydrogen gas, supplied to the anode side is turned into hydrogen ions on a catalytic electrode, and moves to the cathode via the appropriately humidified solid polymer electrolyte membrane. Electrons generated during this electrochemical reaction are taken out to an external circuit, and are used as direct-current electric energy. Since an oxidant gas, for example, an oxygen containing gas or air is supplied to the cathode, the hydrogen ions, the electrons and the oxidant gas react with each other at the cathode, to thereby generate water.
Here, a sealing member is intervened between the membrane electrode assembly and the separators provided at opposite positions on both thereof to ensure airtightness, so that the fuel gas and the oxidant gas supplied to the anode and the cathode do not leak outside, and a reactant gas channel for guiding the fuel gas and the oxidant gas is provided on the surface of the separator, in a portion surrounded by the sealing member (see Japanese Unexamined Patent Application, First Publication No. Hei 8-171926).
The separators of the fuel cell are required to have high conductivity and gastightness with respect to the fuel gas, and hence in many cases, the separators are molded with carbon type materials. However, in order to form the above described reactant gas channel in the carbon type material, there is a problem in that machining such as milling which takes time and energy becomes necessary. In order to deal with such a problem, separators made of a metal material have recently been adopted, as shown for example in Japanese Unexamined Patent Application, First Publication No. 2000-21418.
This will be described with reference to FIG. 19. In FIG. 19, reference symbol I denotes a separator (anode side separator) made of stainless steel which is formed by press forming. On the upper and lower parts of the left side edge and the right side edge of the separator 1, there are formed communicating holes 2 and 3. The communicating holes 2 and 3 are allocated for the inlet side and the outlet side of the fuel gas and the oxidant gas, respectively, and a plurality of separators are laminated with the electrolyte membrane electrode assembly clamped between the anode side separator and the other separator (a cathode side separator) (not shown), and an internal manifold is formed penetrating these separators. Moreover, a communicating hole 4 for cooling water is provided between respective communicating holes 2 and 3, so that the cooling water flows in the space between the anode side separator and the adjacent separator arranged on the backside thereof to thereby cool the fuel cell.
On the surface of the separator 1, there are formed a plurality of linear protruding members 5 by applying a corrugating process by press forming. These protruding members 5 are for supplying the fuel gas to grooves formed between adjacent protruding members, and guide the fuel gas supplied from the communicating hole 2 on the inlet side to the communicating hole 2 on the outlet side at diagonally opposite positions, so that the reaction with the oxidant gas (not shown) is performed uniformly.
At positions surrounding the communicating holes 2 and the protruding members, there is provided a gasket portion 6 made of resin or rubber, and this gasket portion 6 seals between the anode side separator and the membrane electrode assembly (not shown in the figure) to thereby ensure the airtightness with the outside, The gasket portion 6 is provided with connecting portions 6a directed towards the protruding members 5 with a predetermined interval, and these connecting portions 6a are connected to the protruding members 5 to form a meandering reactant gas channel for the fuel gas supplied from the communicating hole 2, with a plurality of protruding members 5 being collected as one unit.
In the above described prior art, by using the press-formed separator made of a metal, the separator can be manufactured within a short period of time, compared to the case where it is manufactured by cutting or the like, and this is advantageous in view of strength, but there is a problem in that position adjustment between the connecting portions 6a and the protruding members 5, in particular, height adjustment is difficult. If the connecting portions 6a overlap on the protruding portions 5, these overlapped portions rise up, and as a result, the electrolyte membrane electrode assembly is damaged. On the other hand, if a gap is formed between the connecting portions 6a and the protruding portions 5, gas leakage occurs thereby decreasing the reaction efficiency.
Moreover, if a strict dimensional accuracy control is performed so that the above described gap is not formed, there is a problem in that the manufacturing process becomes complicated as a whole, even if the productivity of the separator itself is improved by means of the press forming.